My own content-filtering web app?

Hello

There's a site that I use often that's a bit on the heavy site and doesn't provide a smartphone application.

So I was thinking of writing some simple web application (in Python) that would simply act at the man-in-the-middle and smartphones would have access to a lighter and faster version of the original site.

http://imageshack.us/photo/my-images/191/webproxyapp.png/

But the original site relies on a session cookie to keep track of logged-on users. Are there other common issues when writing some kind of web proxy application?